Authentication in a Basic Architecture

Figure 21–2 shows the interaction
of the software components in the authentication process of a basic architecture
of Instant Messaging. The focus is on the flow of authentication requests.
An explanation of the steps in this process follows the figure.

The login window appears and the end user enters the login
name and password. The login data is sent to the Instant Messaging server
through the multiplexor.

The Instant Messaging server communicates with the LDAP server
to authenticate the end user and to request end-user information, such as
contact lists or subscriptions.

When the end-user authentication is complete, the Instant Messaging
main window appears, displaying the contact list for the end user. The end
user can now start and participate in Instant Messaging sessions with the
other end users.